Rugged, gel-free, lithium-free, high energy density solid-state electrochemical energy storage devices

ABSTRACT

Described are solid-state electrochemical energy storage devices and methods of making solid-state electrochemical energy storage devices in which components of the batteries are truly solid-state and do not comprise a gel. Nor do they rely on lithium-containing electrolytes. Electrolytes useful with the solid-state electrochemical energy storage described herein include, for example, ceramic electrolytes exhibiting a crystal structure including voids or crystallographic defects that permit conduction or migration of oxygen ions across a layer of the ceramic electrolyte. Disclosed methods of making solid-state electrochemical energy storage devices include multi-stage deposition processes, in which an electrode is deposited in a first stage and an electrolyte is deposited in a second stage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication No. 62/233,785, filed on Sep. 28, 2015. This application isalso a continuation-in-part of U.S. Application No. 13/536,029, filed onJun. 28, 2012, now abandoned, which claims the benefit of and priorityto U.S. Provisional Application No. 61/502,797, filed Jun. 29, 2011. Theentire disclosures of the above applications are hereby incorporated byreference, for all purposes, as if fully set forth herein.

FIELD

The present invention relates to electrochemical energy storages devicehaving no close precedent in the prior art and methods for makingelectrochemical energy storage devices. The devices diverge from theprior art in their scale, physical construction and geometry, chemistry,electrical behaviors, and applications.

CONSTRAINTS ON THE PERFORMANCE OF THE CURRENT ART

Hundreds of developed battery chemistries and architectures exist, andthere is likewise an extreme diversity in terms of cycle life, storagecapacity, robustness, stability, and cost. Nevertheless, certaincommonalities emerge after careful consideration of the many variants.

Conventional batteries exhibit high energy densities compared to mostother methods of energy storage, but perform very poorly compared tocombustible sources of energy such as fossil fuels, alcohols, andhydrogen gas, all of which exceed conventional batteries by manymultiples in this regard. This has important implications with regard topowered portable devices and electric traction.

Conventional batteries have low power density compared to bothcapacitors and high velocity flywheels. Their ability to followfluctuating electrical loads and complex electrical impedances istherefore limited as well.

Some secondary batteries are based upon purportedly reversibleelectrochemical reactions, but they are not, in fact, fully reversiblein any practical sense. Secondary batteries characteristically losestorage capacity over time, and exhibit degradation of their componentparts as they undergo repeated charging and discharging. For example,secondary batteries may exhibit a loss in capacity due to destruction ofthe electrolyte, the anode, or the cathode. Overcharging and fullydischarging secondary batteries may also cause capacity loss. In extremecases, secondary batteries, such as lithium-based secondary batteries,may also exhibit a short circuit and rapidly discharge and heat and evencatch fire. Additionally, exposure of many secondary batteries toelevated temperatures may also degrade various components and result incapacity loss. Thus, secondary batteries, for the most part, cannot befully discharged without damage, degradation, and a considerableabbreviation of their useful working lives. Conversely, they cannottolerate overcharging.

Conventional batteries are subject to electrical leakage and chargedissipation and cannot maintain a given state of charge indefinitely oreven over a span of weeks. Such dissipation can eventually lead to fulldischarge and damage to the battery.

Conventional batteries cannot be charged instantaneously or evenparticularly quickly. Presenting conventional batteries with anexcessive charging current in an effort to accelerate the chargingprocess will generally damage the device. Moreover, charging with anyrapidity entails a complex charging algorithm and an intelligentinterface, increasing system complexity.

Conventional batteries, for the most part, are comprised of liquidsand/or gels which do not lend themselves to precision manufacturing orextreme reductions in scale, and which may be subject to leakage and/orevaporation, and which require external containment vessels.

Conventional batteries do not thrive in extreme temperatureenvironments. With the exception of the small subset of high temperaturebatteries, such as sodium sulfur and lithium sulfur types, almost nonecan endure temperatures of even a hundred degrees Celsius, whileoperation at zero degrees Celsius and below results in greatlydiminished capacity and sluggish performance.

Conventional batteries are low voltage devices, with 4 voltsrepresenting the maximum operating potential of any establishedchemistry, and 2 volts or less being more representative. Such a voltagerange is impractically low for many applications, and thus batterymanufacturers must resort to connecting a number of individual cells inseries to achieve higher voltages. Balancing such series of cells can bedifficult due to normal cell-to-cell variation in electrical output.Individual cell failure can also result in lost capacity and diminishedusability.

Most of the established conventional battery chemistries appear to beapproaching the ends of their respective development cycles and havebeen subject to diminishing returns in terms of performanceimprovements.

Such deficiencies are attributable both to the chemistries themselves,the design and articulation of the electrodes and their interface withthe electrolyte material, and with the way that traditional fabricationtechniques have tended to dictate architecture.

SUMMARY

Devices for electrochemically storing energy at a high density aredescribed. Methods of making electrochemical energy storage devices arealso described. In embodiments, the electrochemical energy storagedevices correspond to an all solid-state construction, and do notinclude any gels, liquids, or other materials that are incompatible withmicrofabrication techniques, such as may be used in the fabrication ofintegrated circuits and photovoltaic devices.

In a first aspect, an electrochemical energy storage device embodimentcomprises a first electrode, a solid electrolyte positioned in directcontact with the first electrode, and a second electrode positioned indirect contact with the solid electrolyte. It will be appreciated thatthe first and second electrodes may be positioned such that the solidelectrolyte is between the first and second electrodes.

Various aspects of the electrodes may take on different configurations,depending on the particular embodiments utilized. For example, in someembodiments, a variety of electrode thicknesses are useful with theelectrochemical energy storage devices. For example, in embodiments, thefirst electrode and the second electrode independently have thicknessesselected between about 1 nm and about 5 nm, between about 1 nm and about10 nm, between about 1 nm and about 15 nm, between about 1 nm and about20 nm, between about 1 nm and about 25 nm, between about 1 nm and about30 nm, between about 1 nm and about 35 nm, between about 1 nm and about40 nm, between about 1 nm and about 45 nm, between about 1 nm and about50 nm, between about 1 nm and about 55 nm, between about 1 nm and about60 nm, between about 1 nm and about 65 nm, between about 1 nm and about70 nm, or between about 1 nm and about 75 nm. Optionally, an electrodethickness is about 5 nm, about 10 nm, about 15 nm, about 20 nm, about 25nm, about 30 nm, about 35 nm, about 40 nm, about 45 nm, about 50 nm,about 55 nm, about 60 nm, about 65 nm, about 70 nm, about 75 nm, about80 nm, about 85 nm, about 95 nm, or about 100 nm. It will beappreciated, however, that electrodes of any thickness greater than orabout 1 nm may be utilized for some embodiments.

In some embodiments, the electrodes may have independent chemicalstructures. For example, in some embodiments, the first electrode andthe second electrode independently comprise oxides of a metal selectedfrom the group consisting of Fe, Co, Ni, Cu, Mo, Tc, Rh, Pd, Ag, W, Re,Os, Ir, and Pt. Optionally, the first electrode and the second electrodeindependently comprise oxides of a metal selected from the groupconsisting of Mn, Fe, Co, Ni, Cu, Mo, Tc, Ru, Rh, Pd, Ag, W, Re, Os, Ir,and Pt. In some embodiments, an electrode comprises the same metal oxideas another electrode. In other embodiments, an electrode comprises adifferent metal oxide as another electrode.

In some embodiments, using particular metals or metal oxides for theelectrodes may be advantageous, as certain metals and metal oxides mayexhibit desirable properties. For example, in some embodiments, anelectrode is capable of undergoing reversible redox reactions to gain orlose oxygen atoms at a respective electrode surface during charging ordischarging. As another example, in some embodiments, a metal of anelectrode is capable of forming sequences of metal oxides ofprogressively greater molecular weight at a respective electrodesurface. Optionally, an electrode undergoes electrochemical oxygenadsorption during charging of the solid-state energy storage device.Optionally, an electrode undergoes electrochemical oxygen desorptionduring charging of the solid-state energy storage device. Optionally, ametal of an electrode exhibits a work function of between about 4 eV andabout 5 eV.

In some embodiments, the oxide of the metal of an electrode is dispersedon an electrically conductive supporting matrix. For example, inembodiments, the electrically conductive supporting matrix may comprisecarbon, graphite, or other materials that may provide electricalconductivity while also providing a platform for deposition of theelectrode material. In embodiments, use of an electrically conductivesupporting matrix may be advantageous for increasing a surface area ofthe metal or metal oxide of the electrode to increase the electrode massthat may take part in electrochemical redox reactions when chargingand/or discharging the electrochemical storage devices.

Optionally, electrodes may be independently fabricated using acontrollable deposition method. Useful deposition techniques include,but are not limited to, atomic layer deposition, magnetron sputtering,and chemical vapor deposition. Other fabrication techniques useful forfabricating the electrodes may include or involve other techniques, suchas ultraviolet lithography, x-ray lithography, holographic lithography,laser ablation, and thermal evaporation.

Various aspects of the solid electrolyte may take on differentconfigurations, depending on the particular embodiments utilized. Forexample, in some embodiments, a variety of electrolyte thicknesses areuseful with the electrochemical energy storage devices. For example, inembodiments, an electrolyte has a thickness selected between about 1 nmand about 5 nm, between about 1 nm and about 10 nm, between about 1 nmand about 20 nm, between about 1 nm and about 50 nm, between about 1 nmand about 100 nm, between about 1 nm and about 150 nm, between about 1nm and about 200 nm, or between about 1 nm and about 250 nm. Otherelectrolyte thicknesses may be useful for some embodiments, thoughelectrolyte thicknesses less than or about 250 nm may be preferable forcertain embodiments. In some embodiments, for example, an electrolytehas a thickness selected between about 1 nm and about 300 nm, betweenabout 1 nm and about 350 nm, between about 1 nm and about 400 nm,between about 1 nm and about 450 nm, between about 1 nm and about 500nm, between about 1 nm and about 550 nm, or between about 1 nm and about600 nm.

As the electrolyte thickness is increased, embodiments may experiencereduced device performance. For example, depending on the embodiment, anelectrolyte thickness may correlate with the ionic conductivity of theelectrolyte. At some particular thickness, however, the electrolyte mayexhibit a dramatic decrease in ionic conductivity, making such anelectrolyte unsuitable for use in an electrochemical energy storagedevice. For example, depending on the particular electrolyte compositionused in some embodiments, the maximum useful electrolyte thickness maybe about 500 nm, about 550 nm, about 600 nm, about 650 nm, or less thanabout 700 nm. Each particular electrolyte composition may exhibit a“cut-off” thickness value above which the electrolyte exhibitsconductivity properties comparable to the bulk, such as where an ionicconductivity is unsuitable for use in an electrochemical energy storagedevice, and below which the electrolyte exhibits conductivity propertiesdifferent from the bulk, such as where the ionic conductivity is about10× greater or more, about 100× greater or more, about 1000× greater ormore, about 10000× greater or more, or about 100000× greater or morethan the ionic conductivity of the electrolyte in the bulk. In someembodiments, a solid electrolyte exhibits an oxygen ion conductivity atabout 25° C. that is about 1000 times greater or more than a bulk oxygenion conductivity for the solid electrolyte. Optionally, the bulk oxygenion conductivity for the solid electrolyte corresponds to a conductivityof oxygen ions at about 25° C. for the solid electrolyte having athickness greater than about 700 nm. Optionally, at about 25° C., thesolid electrolyte exhibits an ion conductivity for oxygen ions selectedfrom the range of about 0.000001 S·cm⁻¹ to about 0.2 S·cm⁻¹, or whereinthe solid electrolyte exhibits an ion conductivity for oxygen ions inexcess of about 0.00001 S·cm⁻¹ at about 25° C.

In embodiments, various materials properties of the solid electrolyteallow for migration of ions across the solid electrolyte, making thesolid electrolyte suitable for use in an electrochemical energy storagedevice. It will be appreciated that certain solid electrolytes mayexhibit ionic conductivity properties at high temperatures, such as attemperatures of about 600° C., which would otherwise be suitable for usein an electrochemical energy storage device, except that the temperatureis impractical to achieve, maintain, or use. Electrochemical energystorage devices of the invention, however, maintain suitable ionicconductivity properties even at temperatures at which conventionalbatteries are useful, such as about 25° C. Unlike conventionalbatteries, the electrochemical energy storage devices of the inventionexhibit suitable properties at most temperatures commonly encountered byhumans. For example, the solid-state electrolytes used in theelectrochemical energy storage devices may exhibit suitable ionicproperties at temperatures as low as about −50° C., as well as attemperatures as high as about 50° C. and higher.

Various compositions are useful for the solid electrolytes of theelectrochemical energy storage devices. In embodiments, a solidelectrolyte comprises a ceramic selected from the group consisting of aperovskite ceramic, a ceramic having a perovskite structure, a zirconiumceramic, a ceria-gadolinia ceramic, an alumina ceramic, and anycombination of these. Optionally, the solid electrolyte comprises aceramic selected from the group consisting of a perovskite ceramic, aceramic having a perovskite structure, a zirconium-scandia ceramic, aceria-gadolinia ceramic, an alumina ceramic, and any combination ofthese. Optionally, a solid electrolyte comprises a crystalline ceramic,such as a single crystalline or polycrystalline ceramic material.

Optionally, the solid electrolyte comprises a composite solidelectrolyte including a plurality of different ceramics. For example thesolid electrolyte may comprise layers of different ceramic materials. Inembodiments, strained solid electrolytes may exhibit higher ionicconductivities than unstrained solid electrolytes and, thus, impartingstrain on a solid electrolyte may provide for a way to increase theionic conductivity of the solid electrolyte to a level suitable for usein a solid-state electrochemical energy storage device. In embodiments,introducing stress or strain into the electrolyte may result in thegeneration of voids or crystallographic defects. Use of composite solidelectrolytes may be useful, in embodiments, to impart strain or stresson the solid electrolyte materials, as different solid electrolytematerials may exhibit different thermal expansion properties. Inembodiments, the solid electrolytes may be formed at high temperaturesand then allowed to relax to ambient temperature and the differentexpansion properties may create levels of strain that allow the solidelectrolyte to possess an ionic conductivity suitable for use in anelectrochemical energy storage device. The stress or strain placed onthe electrolyte may, in embodiments, modify the ionic conductivity ofthe electrolyte to increase it to a level beyond that in the unstressedor unstrained condition. Other techniques may be useful for impartingstress or strain to an electrolyte, including exploiting differentthermal expansion characteristics of non-electrolyte materialspositioned proximal to, adjacent to, or in direct contact with theelectrolyte.

Additionally, piezoelectric materials may optionally be positionedproximal to, adjacent to, or in direct contact with the electrolyte andexposed to a potential to cause expansion or contraction of the materialto impart stress or strain on an electrolyte. In some embodiments, useof piezoelectric materials may be beneficial for controlling the amountof ionic conductivity permitted by the electrolyte. For example, anelectrochemical energy storage device may include a solid electrolyte,in some embodiments, which has a relatively low ionic conductivity and apiezoelectric material that is positioned proximal the electrolyte inorder to control the ionic conductivity of the electrolyte, as desired.For example, in some embodiments, the piezoelectric material may beactuated to afford an increase in the electrolyte ionic conductivityduring a charging or discharging cycle, but then be de-actuated orrelaxed while not charging or discharging. Such an embodiment, forexample, may provide a way to prevent or reduce self-discharge of anelectrochemical energy storage device while not in use or in storage.

In some embodiments, a solid electrolyte comprises or exhibits a crystalstructure including voids or crystallographic defects that permitconduction or migration of ions, such as oxygen ions (e.g., oxygenanions), through the solid electrolyte at temperatures between about 0°C. and about 100° C. In some embodiments, the solid electrolytecomprises or exhibits a crystal structure including voids orcrystallographic defects that permit conduction or migration of oxygenions through the solid electrolyte at temperatures outside of thepreviously mentioned range, such as at temperatures less than about 0°C. or greater than about 100° C. As described above, it will beappreciated that this property may be contrasted with the same materialof the solid electrolyte in the bulk, where voids crystallographicdefects present in the bulk material may still not provide for suitableionic conductivity. Optionally, the crystallographic defects correspondto one or more vacancy defects, interstitial defects, boundary defects,line defects, planar defects, bulk defects, or lattice imperfections.Optionally, a solid electrolyte comprises a doped ceramic including oneor more dopants. Useful dopants include, but are not limited to, analkali metal dopant, an alkaline earth dopant, a group 3 dopant, ascandium dopant, a yttrium dopant, a lanthanide dopant, a titanium oxidedopant, a hydrogen dopant, a silver dopant, and a lead dopant.Optionally, a solid electrolyte comprises a heavily doped ceramic, Forexample, in some embodiments a solid electrolyte comprises a ceramicalloy, such as beta alumina.

Optionally, solid electrolytes may be fabricated using a controllabledeposition method. Useful deposition techniques include, but are notlimited to, atomic layer deposition, magnetron sputtering, and chemicalvapor deposition. Other fabrication techniques useful for fabricatingthe electrolytes may include or involve other techniques, such asultraviolet lithography, x-ray lithography, holographic lithography,laser ablation, and thermal evaporation.

It will be appreciated that the solid electrolytes useful with theelectrochemical energy storage devices disclosed herein are differentfrom those used in conventional batteries. For example, in embodiments,the solid electrolyte is free from or does not include any liquids orgels. Additionally, the solid electrolytes are categorically differentfrom those used with lithium-based batteries. For example, lithium-basedbatteries may rely on a lithium containing electrolyte. In embodiments,the solid electrolytes used with the electrochemical energy storagedevices described here are free from or do not include any lithium, suchas lithium atoms, lithium ions, or lithium salts.

Optionally, an electrochemical energy storage device further comprises asecond solid electrolyte positioned in direct contact with the secondelectrode, and a third electrode positioned in direct contact with thesecond solid electrolyte. Optionally, an electrochemical energy storagedevice further comprises one or more solid electrolyte and metal oxideelectrode bi-layers positioned in direct contact with a topmostelectrode. It will be appreciated that the characteristics describedabove may also apply to additional solid electrolytes and electrodes.

In embodiments, the electrochemical energy storage devices may becharged using any suitable voltage. For example, charging voltages maybe higher than used in conventional secondary batteries. For example, inembodiments, a voltage difference between the first electrode and thesecond electrode may be greater than about 1 V, greater than about 2 V,greater than about 4 V, greater than about 8 V, or greater than about 16V. Other voltage differences are possible, including voltages of about0.5 V, about 1 V, about 1.5 V, about 2 V, about 2.5 V, about 3 V, about3.5 V, about 4 V, about 4.5 V, about 5 V, about 5.5 V, about 6 V, about6.5 V, about 7 V, about 7.5 V, about 8 V, about 8.5 V, about 9 V, about9.5 V, about 10 V, about 10.5 V, about 11 V, about 11.5 V, about 12 V,about 12.5 V, about 13 V, about 13.5 V, about 14 V, about 14.5 V, about15 V, about 15.5 V, about 16 V, about 16.5 V, about 17 V, about 17.5 V,about 18 V, about 18.5 V, about 19 V, about 19.5 V, about 20 V, etc.

In embodiments, the solid-state energy storage devices may becharacterized by electrical energy densities comparable to other energystorage devices, such as conventional batteries, and may even exceed theenergy storage densities of conventional batteries. For example, theelectrical energy density of the solid-state energy storage device maybe greater than about 10 J/cm³, greater than about 20 J/cm³, greaterthan about 50 J/cm³, greater than about 100 J/cm³, greater than about150 J/cm³, greater than about 200 J/cm³, greater than about 250 J/cm³,greater than about 300 J/cm³, greater than about 350 J/cm³, greater thanabout 400 J/cm³, greater than about 450 J/cm³, or greater than about 500J/cm³, etc.

In contrast to conventional batteries, the disclosed energy storagedevices may be included in an integrated circuit, microelectromechanicalsystem, or other system assembled using microfabrication tools. Forexample, in embodiments, the first electrode, the solid-stateelectrolyte, and the second electrode are components of an integratedcircuit. Optionally, one or more circuit elements of the integratedcircuit are positioned in electrical communication with the firstelectrode or the second electrode such that the one or more circuitelements receive electrical energy stored by the solid-state energystorage device. It will be appreciated that electrical communication maybe direct or indirect.

In addition, the disclosed electrochemical energy storage devices may beincluded as a component of a photovoltaic system. For example, inembodiments, the first electrode, the solid-state electrolyte, and thesecond electrode are integrated with a photovoltaic cell or areintegrated components of a photovoltaic system. For example, in someembodiments, the first electrode, the solid-state electrolyte, and thesecond electrode may be deposited on a substrate that comprises acomponent of a photovoltaic cell. It will be appreciated that variousfabrication processes may be advantageously used for preparation of anelectrochemical energy storage device included as a component of aphotovoltaic system, such as atomic layer deposition, magnetronsputtering, and thermal evaporation. The deposition of variouscomponents of the solid state electrochemical energy storage device mayoptionally be performed at about the same time or subsequent toconstruction of any electrodes needed or used by the photovoltaic cell.In embodiments, electrodes of a photovoltaic cell are positioned inelectrical communication with the first electrode and the secondelectrode such that electrical energy generated by the photovoltaic cellmay be used to charge the electrochemical energy storage device forstorage therein or so that electrical energy stored by the solid-stateenergy storage device may be utilized as needed in place of photovoltaicoutput.

In embodiments, the solid-state electrochemical energy storage devicemay comprise a component of a photovoltaic output management system.Advantageously, the electrochemical energy storage device may optionallystore electrical power generated by a photovoltaic system in excess ofthat consumed by a load otherwise powered by the photovoltaic system,which may occur, for example, during times of peak power production orlow demand. In some embodiments, the energy stored by theelectrochemical energy storage devices may be useful for smoothing theoutput variability of a photovoltaic system over time and may forexample, be useful for maintaining a substantially constant or lessvariable output from the photovoltaic system as energy productionchanges from moment to moment (e.g. due to a passing cloud).Additionally, the stored energy may optionally be provided to and usedby a load connected to the photovoltaic system when the photovoltaicenergy production is lower than that required by the load, such asduring times of high demand, or during night or on cloudy days. In thisway, the electrochemical energy storage device may enhance the utilityof a photovoltaic system by allowing storage of excess energy whengenerated, use of stored energy when insufficient generation occurs, andmaintaining substantially constant output as photovoltaic power ismodulated.

In another aspect, methods of making energy storage devices aredisclosed. In embodiments, methods of this aspect comprise depositing afirst electrode on or over a substrate, such as by using a firstcontrollable deposition method, depositing a solid electrolyte on orover the first electrode, such as by using a second controllabledeposition method, and depositing a second electrode on or over thesolid electrolyte such as by using a third controllable depositionmethod. In some embodiments, additional electrolyte and electrodedeposition processes may be included in the method in order to generateenergy storage devices exhibiting a stacked multilayer configuration.

Useful controllable deposition methods include, but are not limited tothose involving atomic layer deposition, magnetron sputtering, chemicalvapor deposition, ultraviolet lithography, x-ray lithography,holographic lithography, laser ablation, and thermal evaporation.

Optionally, the deposition of the electrodes generates electrodes of adesired thickness, as described above. For example, in embodiments, adeposited electrode thickness is selected from the range of about 1 nmto about 75 nm. Optionally, the electrodes may comprise oxides of one ormore of Fe, Co, Ni, Cu, Mo, Tc, Rh, Pd, Ag, W, Re, Os, Ir, and Pt.Optionally, the electrodes may comprise oxides of one or more of Mn, Fe,Co, Ni, Cu, Mo, Tc, Ru, Rh, Pd, Ag, W, Re, Os, Ir, and Pt.

Optionally, the deposited solid electrolyte comprises one or more of aperovskite ceramic, a ceramic having a perovskite structure, a zirconiumceramic, a ceria-gadolinia ceramic, an alumina ceramic, and anycombination of these. Optionally, the deposited solid electrolytecomprises one or more of a perovskite ceramic, a ceramic having aperovskite structure, a zirconium-scandia ceramic, a ceria-gadoliniaceramic, an alumina ceramic, and any combination of these. Optionally,the deposition of the solid electrolyte generates an electrolyte of adesired thickness, as described above. For example, in embodiments, thesolid electrolyte has a thickness selected from the range of about 1 nmto about 250 nm. In embodiments, the solid electrolyte comprises orexhibits a crystal structure including voids or crystallographic defectsthat permit conduction or migration of oxygen ions through the solidelectrolyte between about 0° C. and about 100° C. Optionally, the solidelectrolyte comprises or exhibits a crystal structure including voids orcrystallographic defects that permit conduction or migration of oxygenions through the solid electrolyte at temperatures less than about 0° C.or greater than about 100° C.

As described above, the solid-state energy storage devices may beincorporated in an integrated circuit. In embodiments, the substrate onwhich an electrode is deposited comprises a component of an integratedcircuit.

In some embodiments, methods of this aspect may include charging and/ordischarging an electrochemical energy storage device. For example, avoltage difference may be applied between the first electrode and asecond electrode, such as a charging voltage, in order to charge theelectrochemical energy storage device. It will be appreciated that, inembodiments, the charging may occur rapidly or substantiallyinstantaneously, such as within a period of seconds or minutes or afraction thereof, depending on the current available from the voltagesource and resistive losses between the voltage source and theelectrodes. This rapid charging may also occur, in embodiments, withoutdamaging the electrodes or electrolyte. This may contrast with thecharging rate of a conventional battery, which may be limited by thekinetics taking place at the battery electrodes or within theelectrolyte, or may be limited because charging at a greater rate mayresult in damage to the structure of the battery, such as electrodedamage or electrolyte damage, and accompanying capacity loss. Inembodiments, the electrochemical reactions that occur when charging ordischarging the electrochemical energy storage devices occur at or nearthe electrode surfaces and so the reactions may occur substantiallyquickly as compared to, for example, intercalation processes orelectroplating processes that may occur in conventional batteries. Highcharge or discharge rates may also or alternatively be aided by thesmall size dimensions used in the electrochemical energy storagedevices, where only a small physical spacing between electrodes exists,allowing ionic migration between the electrodes to occur rapidly. Inembodiments, discharging may occur rapidly or substantiallyinstantaneously, such as within a period of seconds or minutes or afraction thereof. This rapid discharging may also occur, in embodiments,without damaging the electrodes or electrolyte. In embodiments, adischarge rate may be dictated by the resistance of a load appliedbetween the electrodes of the electrochemical energy storage devicesand/or resistive losses between the load and the electrodes. Inembodiments, the electrochemical energy storage devices may be chargedand/or discharged at rates of about C/20, about C/10, about C/5, aboutC/2, about 1 C, about 2 C, about 5 C or about 10 C or more withoutinducing damage to the electrochemical energy storage device, such asdamage characteristic of capacity loss, electrolyte oxidation orreduction, electrode destruction, etc. Charging times may also varydepending on charging voltage, charging current, etc. Example chargingtimes may be less than about 1 second, less than about 10 seconds, lessthan about 30 seconds, less than about 1 minute, less than about 5minutes, less than about 10 minutes, less than about 30 minutes, etc.Beneficially, electrochemical energy storage device embodiments may bedischarged to zero charge stored or zero voltage difference betweenelectrodes without inducing damage to the electrochemical energy storagedevice, such as damage characteristic of capacity loss, electrolyteoxidation or reduction, electrode destruction, etc.

Further, in some embodiments, the electrochemical energy storage devicesexhibit exceptional cycle lives. For example, the electrochemical energystorage devices may be charged and discharged any number of timeswithout inducing damage to the electrochemical energy storage device,such as damage characteristic of capacity loss, electrolyte oxidation orreduction, electrode destruction, etc. For example, the electrochemicalenergy storage devices of some embodiments may be charged and dischargedmore than about 100 times, more than about 1000 times, more than about10000 times, more than about 100000 times, or more than about 1000000times without damaging the electrochemical energy storage device, suchas damage characteristic of capacity loss, electrolyte oxidation orreduction, electrode destruction, etc.

Without wishing to be bound by any particular theory, there can bediscussion herein of beliefs or understandings of underlying principlesrelating to the invention. It is recognized that regardless of theultimate correctness of any mechanistic explanation or hypothesis, anembodiment of the invention can nonetheless be operative and useful.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a plot illustrating the relationship of ionicconductivity and temperature for a variety of solid-state electrolytesin the bulk.

FIG. 2A provides a schematic overview of charging a solid-stateelectrochemical energy storage device and FIG. 2B provides a schematicoverview of discharging a solid-state electrochemical energy storagedevice.

FIG. 3 provides a schematic illustration of processes taking placewithin a solid-state electrochemical energy storage device.

FIG. 4A and FIG. 4B provide overviews of processes for makingsolid-state electrochemical energy storage devices.

FIG. 5 provides a schematic illustration of the crystal structure of asolid electrolyte, in accordance with some embodiments.

FIG. 6 provides a schematic illustration of the crystal structure of asolid electrolyte, in accordance with some embodiments.

FIG. 7 provides a schematic illustration of a system includingelectrochemical energy storage devices distributed throughout thecircuit.

FIG. 8 provides a schematic illustration of a multilayer electrochemicalenergy storage device.

FIG. 9 provides a schematic cross-sectional illustration of anintegrated circuit including multilayer electrochemical energy storagedevices.

FIG. 10A and FIG. 10B provides schematic cross-sectional illustrationsof an photovoltaic device including multilayer electrochemical energystorage devices.

DETAILED DESCRIPTION

The present application provides electrochemical energy storage devicesand methods of making these devices. The devices are based on a uniquearchitecture involving a pair of metal or metal oxide electrodes with asolid-state electrolyte (also referred to herein as a solid electrolyte)positioned in between the electrodes. For example, the metal or metaloxide electrodes may correspond to certain transition metals or metaloxides. For example, the solid-state electrolyte may correspond tocertain ceramics capable of conducting ions through their crystalstructure.

Advantageously, electrochemical energy storage device embodiments may beof an entirely solid-state construction. For example, all electricallyactive layers may also provide structural functions, such that theelectrochemical energy storage device is not only entirelyself-supporting but capable of reinforcing other elements to which it isconjoined.

FIG. 1 provides details of the ionic conductivity of a number ofsolid-state ceramic materials in the bulk. It will be appreciated thatthe conductivity of most of these materials only reaches appreciablevalues at temperatures exceeding about 300° C. At room temperature, theconductivity values of these ceramic materials are extremely small,making them very effective insulating materials.

The inventors have discovered, however, that thin films of certainsolid-state ceramic materials, such as films having thickness of lessthan about 700 nm in some embodiments, may be engineered to exhibit highionic conductivity at room temperature. This property allows thesolid-state ceramics to function as electrolyte materials, and toexploit this engineered characteristic to permit transmission of ions.Such observation is entirely contrary to the electrical behavior of thesolid-state ceramics in the bulk described above.

The conduction of ions through the solid-state electrolyte provides thebasis for charge storage in some embodiments disclosed herein. FIG. 2Aand FIG. 2B provides schematic overviews of charging (FIG. 2A) anddischarging (FIG. 2B) of an example solid-state electrochemical chargestorage device 200. Here, solid-state electrochemical charge storagedevice 200 includes a first electrode 210, an electrolyte 220, and asecond electrode 230. As shown in FIG. 2A, during a charging operation,anions may be driven from the first electrode 210, through theelectrolyte 220, to second electrode 230, while cations may be drivenfrom the second electrode 230, through the electrolyte 220, to firstelectrode 210. As shown in FIG. 2B, during a discharging operation,cations may be driven from first electrode 210, through the electrolyte220, to second electrode 230, while anions may be driven from the secondelectrode 230, through the electrolyte 220, to first electrode 210. Itwill be appreciated that in some embodiments only a single anionicspecies may correspond to the working ion, while in other embodimentsonly a single cationic species may correspond to the working ion.Embodiments are contemplated, however, where multiple ionic species arethe working ions, such as multiple anionic species, multiple cationicspecies, or combinations of anionic species and cationic species. Suchidentities will be established by the specific chemistry utilized in aspecific electrochemical energy storage device.

As depicted in FIG. 2A, during charging, electrons may be provided by avoltage source 240 to the first electrode 210. In embodiments whereoxygen anions (O²⁻) correspond to the working ion, the electrons may beused in a reduction reaction at the first electrode where oxygen anionsmay be released. The oxygen anions may be conducted through the solidelectrolyte 220 to the second electrode 230, where they may be taken upby the second electrode and electrons may be released to the voltagesource in an oxidation reaction. It will be appreciated that the energyrequired for the redox reactions, provided by the voltage source, maycorrespond, at least in part, to the energy electrochemically stored bythe electrodes. Other energy storage mechanisms may also contribute tothe energy stored by the system, including capacitive energy storageand/or inductive energy storage. Physical/chemical changes to theelectrodes may be observed during charging. For example, in embodiments,the first electrode 210 will undergo loss of oxygen atoms and the secondelectrode 230 will undergo gain of oxygen atoms during charging.

FIG. 2B depicts discharging of the solid-state electrochemical energystorage device 200. The stored energy may be used during discharging bya load 250. In embodiments where oxygen anions (O²⁻) correspond to theworking ion, the electrons passed through the load 250 may be used in areduction reaction at the second electrode where oxygen anions may bereleased. The oxygen anions may be conducted through the solidelectrolyte 220 to the second electrode 230, where they may be taken upby the second electrode and electrons may be released to the voltagesource in an oxidation reaction. It will be appreciated that the energyused by the load may correspond, at least in part, to energyelectrochemically stored by the electrodes, but other energy storagemechanisms may also contribute, such as capacitive energy storage and/orinductive energy storage. Physical/chemical changes to the electrodesmay also be observed during discharging. For example, in one embodiment,the first electrode 210 will undergo gain of oxygen atoms and the secondelectrode 230 will undergo loss of oxygen atoms during discharging.

FIG. 3 provides a schematic overview of charging and discharging of anelectrochemical energy storage device where oxygen anions correspond tothe working ion. The electrochemical energy storage device of FIG. 3includes a first electrode 310, a solid electrolyte 320, and a secondelectrode 330. As illustrated first electrode 310 includes an oxide(M1O_(A)) of a first metal, M1, and second electrode 330 includes anoxide (M2O_(B)) of a second metal M2. It will be appreciated that thetwo metals may be the same or different and the levels of oxygen presentin the different electrodes may also be the same or different.

Additionally, each electrode optionally includes a conductive supportingmatrix, in which the metals are distributed. In some embodiments, theconductive supporting matrix may correspond to a carbonaceous material,such as carbon black or graphite, for example. Inclusion of a conductivesupporting matrix may be useful for increasing a usable surface area ofan electrode. In some embodiments, only a thin layer of the electrodemay take part in electrochemical reactions, and so increasing thesurface area of the electrode may allow for an increase in the overallamount of the electrode that may take part in the electrochemicalreactions.

In the uncharged configuration, bound oxygen atoms may be included inthe first electrode 310, the solid electrolyte 320, and the secondelectrode 330. During charging, however, some of the oxygen atoms maybecome unbound, such as due to the addition of electrons to the firstelectrode 310, where the oxygen atoms may become free ions, such asoxygen anions (O²⁻). These oxygen anions may move from first electrode310 into the solid electrolyte 320. Oxygen ions added to the solidelectrolyte 320 may migrate through the solid electrolyte 320 and passto the second electrode 330. In some circumstances, the oxygen anionsadded to the solid electrolyte 320 may become bound in the structure ofthe solid electrolyte 320 and a different oxygen atom may be releasedfrom the structure of the solid electrolyte 320 as an oxygen anion,creating an effective migration of the oxygen anion through the solidelectrolyte. The oxygen ions that are added to the second electrode 330may be incorporated into the structure of the second electrode 330.

In the charged configuration, the amounts of oxygen in the firstelectrode 310 and the second electrode 330 may be different from that inthe uncharged configuration. As illustrated, after charging the firstelectrode 310 may have fewer oxygen atoms included in the structure, ascompared to the structure of the first electrode 310 in the unchargedstate. Similarly, as illustrated, after charging the second electrode330 may have more oxygen atoms included in the structure, as compared tothe structure of the first electrode 330 in the uncharged state. Thus,the first electrode 310 is illustrated as having a formula of M1O_(A+Δ),while the second electrode is illustrated as having a formula M2O_(A−Δ).

During discharging, the opposite migration of oxygen occurs. Some of theoxygen atoms in the second electrode 330 may become unbound, such as dueto the addition of electrons, and the unbound oxygen atoms may becomeoxygen anions. These oxygen anions may move from third electrode 330into the solid electrolyte 320. Oxygen ions added to the solidelectrolyte 320 may migrate through the solid electrolyte 320 and passto the first electrode 310. The oxygen ions that are added to the firstelectrode 310 may be reincorporated into the structure of the firstelectrode 310

Advantageously, for certain embodiments, each electrode may be used asan anode or a cathode, depending on a charging configuration used wheninitially charging the electrochemical energy storage devices. Forexample, a first of the two electrodes may be connected to a negativeterminal of a voltage source and a second of the two electrodes may beconnected to a positive terminal of the voltage source during chargingof the electrochemical energy storage device. After charging, the firstelectrode may function as an anode and the second electrode may functionas the cathode. Upon discharging, the electrochemical energy storagedevice may be recharged in the opposite configuration, i.e., where thefirst electrode may be connected to the positive terminal of the voltagesource and the second electrode may be connected to the negativeterminal of the voltage source. After this charging cycle, the firstelectrode may function as the cathode and the second electrode mayfunction as the anode.

This advantageous configuration may be achieved, in embodiments, by thecharge storage mechanism and the chemistry involved. For example, inembodiments, the electrodes may comprise an oxide of the same metal,though levels of oxidation of each of the electrodes may be differentand may change during charging and discharging. For example, in aspecific embodiment, the electrodes may both comprise an iron oxide.Other examples are possible, including where different metals or metaloxides comprise the different electrodes.

As noted above, in some embodiments, only a small layer of the electrodeproximal to the electrolyte may experience significant changes inoxidation state. For example, oxygen ions may be driven to or obtainedfrom shallow depths in the electrodes, in some embodiments, such as afew nm. Accordingly, it may be desirable to form the electrodes as thinas practical so as not to include excess electrode material that isincapable of taking part in electrochemical reactions. Thus, in someembodiments, the electrode thickness may range from about 1 nm to about10 nm, about 1 nm to about 15 nm, from about 1 nm to about 20 nm, about1 nm to about 25 nm, from about 1 nm to about 30 nm, about 1 nm to about35 nm, from about 1 nm to about 40 nm, about 1 nm to about 45 nm, fromabout 1 nm to about 50 nm, about 1 nm to about 55 nm, from about 1 nm toabout 60 nm, about 1 nm to about 65 nm, from about 1 nm to about 70 nm,about 1 nm to about 75 nm. In embodiments, the electrochemical energystorage devices can operate using electrodes of any thickness, includingelectrodes thicker than about 75 nm, but as noted above, suchthicknesses may not be the most efficient use of the electrode materialand may contribute weight to the electrochemical energy storage devicewhile not contributing to the energy storage capacity.

Advantageously, the disclosed electrochemical charge storage devices mayoperate under a variety of different voltage regimes. For example, aninitial charging operation may correspond to a first reduction of metalin an anode such that oxygen anions are released by the anode to thesolid electrolyte. The oxygen anions may take part in a reaction at thecathode where oxygen anions are adsorbed or otherwise taken up by thecathode to form metal oxides. The cathode will thus be in a moreoxidized state after charging. This oxidation may take on differentlevels as more and more oxygen is driven into the cathode duringcharging.

Use of certain metals in the cathode may benefit from this increasedoxidation, as some metal species are capable of exhibiting differentoxidation states. In the case of iron, for example, iron atoms exhibitoxidation states of +1, +2, +3, +4, +5, and +6, though the oxidationstates of +2 and +3 may be the most common. If the electrode comprisesFe, a first charging stage may result in electrochemical creation in thecathode of FeO at a first charging voltage. As the FeO becomes saturatedwith oxygen, a second charging stage may occur, where the FeO becomesfurther oxidized to form Fe₂O₃. This process may continue, with thecreation of Fe₃O₄, Fe₅O₆, Fe₆O₇, etc., each formed at increasingcharging voltages. It will be appreciated that iron is used here forillustrative purposes and that other metals, such as Mn, Co, Ni, Cu, Mo,Tc, Ru, Rh, Pd, Ag, W, Re, Os, Ir, and/or Pt, may be preferable for useas electrodes, though the principal of the operation of the energystorage device by creation of different oxides at increasing voltagesmay be applicable. Table 1 and Table 2 respectively summarize differenthalf reactions that may take place during charging and discharging insome embodiments.

It will be appreciated that this increasing oxidation mechanism mayallow the electrochemical energy storage devices, in embodiments, to becharged to high voltages, such as where the charged voltage correspondsto a voltage difference between a voltage of a first electrode and avoltage of a second electrode proximal where a single solid electrolyteis positioned between the first and second electrodes. Such chargingvoltages may be considerably higher than allowed by previous batterychemistries. For example, in embodiments, the electrochemical energystorage devices may be charged to a voltage between about 0 V and about0.5 V, between about 0 V and about 1 V, between about 0 V and about 1.5V, between about 0 V and about 2 V, between about 0 V and about 2.5 V,between about 0 V and about 3 V, between about 0 V and about 3.5 V,between about 0 V and about 4 V, between about 0 V and about 4.5 V,between about 0 V and about 5 V, between about 0 V and about 5.5 V,between about 0 V and about 6 V, between about 0 V and about 6.5 V,between about 0 V and about 7 V, between about 0 V and about 7.5 V,between about 0 V and about 8 V, between about 0 V and about 8.5 V,between about 0 V and about 9 V, between about 0 V and about 9.5 V, orbetween about 0 V and about 10 V. In some embodiments, theelectrochemical energy storage devices may be charged to a voltagegreater than about 5 V, greater than about 10 V, greater than about 15V, or greater than about 20 V. It will be appreciated that, in someembodiments, as higher and higher voltages are encountered, anelectrical discharge may occur between electrodes and through the solidelectrolyte, resulting in loss of stored charge and potential damage tothe devices.

TABLE 1 Overview of redox chemistry during charging Anode Half ReactionCathode Half Reaction Stage 1 Charging M1O_(X) + 2e⁻ → M1O_(X−1) + O²⁻M2O_(Y) + O²⁻ → M2O_(Y+1) + 2e⁻ Overall Reaction: M1O_(X) + M2O_(Y) →M1O_(X-1) + M2O_(Y+1) Stage 2 Charging M1O_(X−1) + 2e⁻ → M1O_(X−2) + O²⁻M2O_(Y+1) + O²⁻ → M2O_(Y+2) + 2e⁻ Overall Reaction: M1O_(X−1) +M1O_(Y+1) → M2O_(X−2) + M2O_(Y+2) . . . Stage N Charging M1O_(X−(N−1)) +2e⁻ → M1O_(X−N) + O²⁻ M2O_(Y+(N−1)) + O²⁻ → M2O_(Y+N) + 2e⁻ OverallReaction: M1O_(X−(N−1)) + M2O_(Y+(N−1)) → M1O_(X−N) + M2O_(Y+N)

TABLE 2 Overview of redox chemistry during discharging Anode HalfReaction Cathode Half Reaction Stage 1 Discharging M1O_(X) + O²⁻ →M1O_(X+1) + 2e⁻ M2O_(Y) + 2e⁻ → M2O_(Y−1) + O²⁻ Overall Reaction:M1O_(X) + M2O_(Y) → M1O_(X+1) + M2O_(Y−1) Stage 2 DischargingM1O_(X+1) + O²⁻ → M1O_(X+2) + 2e⁻ M2O_(Y−1) + 2e⁻ → M2O_(Y−2) + O²⁻Overall Reaction: M1O_(X+1) + M2O_(Y−1) → M1O_(X+2) + M2O_(Y−2) . . .Stage N Discharging M1O_(X+(N−1)) + O²⁻ → M1O_(X+N) + 2e⁻M2O_(Y−(N−1)) + 2e⁻ → M2O_(Y−N) + O²⁻ Overall Reaction: M1O_(X+(N−1)) +M2O_(Y−(N−1)) → M1O_(X+N) + M2O_(Y−N)

Optionally, a solid-state electrochemical energy storage device isfabricated by means of atomic layer deposition, a form of chemical vapordeposition involving precursor chemicals and a two stage depositionprocess where the deposition chamber must be purged between processingstages. Atomic layer deposition (ALD) permits the formation of layershaving a thickness of several nanometers or less and intricate surfacefeatures of similar dimensions. Advanced magnetron sputtering may alsocorrespond to a useful deposition technique. Multiple depositionchambers may be useful for performing sequential deposition operations.

It will be appreciated that the above reference to ALD does not precludethe use of other nanofabrication techniques applicable tomicro-circuitry either extant or in development, including CVD, thermalevaporation, epitaxial techniques, ultraviolet or X-ray lithography,holographic lithography, thermal evaporation, laser ablation ordeposition.

In exemplary embodiments, individual sandwiches or cells compriseelectrolytic layers alternating with metal or metal oxide electrodes.Actual charge storage occurs within the electrodes, such as by a processin which oxygen ions are adsorbed on or within the electrodes.

The benefits of the ALD and advanced magnetron sputtering fabricationtechnique useful with embodiments described herein are several. Forexample, they permit a high degree of consistency and repeatability andthus a low defect rate. In addition, because they support the formationof three dimensional, high radius features at very small scales, itpermits the designer to increase interfacial surface area by manymultiples over that afforded by featureless flat surfaces within thesame volume. For example, surfaces having contoured topologies thatprovide increased surface area are useful with various embodiments.

In addition, cells of various embodiments may be built up incrementally,layer by layer. Capacity within a given footprint may be optionallycontrolled by varying the number of layers and the dimension of depth.The disclosed solid-state electrochemical energy storage devices furtherlend themselves to the construction of power distribution networks wherethe electrochemical energy storage devices are made modular and modulesare interspersed with active circuitry or transducers. It will beappreciated that strategic depositions performed according to the ALDprocess or advanced magnetron sputtering can support such architectures.Optionally, the number of modules within such overall architectures maybe arbitrarily small or large in number, such as 2 or 3 or as many asabout 10 or more than about 10. Modules residing within sucharchitectures may collectively assume the form of star and hub networks,redundant rings, or meshes, for example.

It will be appreciated that, in embodiments, the term “gel” refers to anon-fluid colloidal network or polymer network that is expandedthroughout its whole volume by a fluid. As used herein, gels areexpressly excluded from consideration as solid materials. Exampleelectrolytes that comprise a gel include, but are not limited to,Nafion, LiPON, etc., which may be used, for example, in thin filmlithium batteries. In some embodiments, electrolytes that comprise a gelcannot be prepared by high temperature deposition methods. It will beappreciated that solid-state electrolytes that comprise a gel cannot beprepared by atomic layer deposition. In addition, electrolytes thatcomprise a gel cannot withstand exposure to temperatures exceeding, forexample 100° C., 200° C., 300° C., etc., without undergoing substantialdamage to the electrolyte structure and/or without resulting in asubstantial decrease in the ionic conductivity of the electrolytestructure.

FIG. 4A provides an overview of a process for making an electrochemicalenergy storage device, in accordance with some embodiments. Initially, asubstrate 405 is subjected to a deposition process 408, such as anatomic layer deposition process, where material of a first electrode 410is deposited onto substrate 405. Use of atomic layer depositionprocesses is advantageous for controlling the thickness of firstelectrode 410. Substrate 405 may correspond to any suitable substrate.As an example, substrate 405 may correspond to a portion of anintegrated circuit, for example. Substrate 405 may alternativelycorrespond to a topmost layer of another electrochemical energy storagedevice.

Next, first electrode 410 is subjected to a second deposition process413, in order to form a solid electrolyte 420 over the first electrode410. For example, second deposition process 413 may correspond to anatomic layer deposition process to form a ceramic solid electrolyte. Useof atomic layer deposition processes is advantageous for controlling thethickness of solid electrolyte 420, as is advanced commercialsputtering.

Next, solid electrolyte 420 is subjected to a third deposition process423, such as an atomic layer deposition process, where material of asecond electrode 430 is deposited onto the solid electrolyte 420. Use ofatomic layer deposition processes is advantageous for controlling thethickness of second electrode 430, as is advanced commercial sputtering.

Certain properties of the electrochemical energy storage systemsdescribed herein are strongly interrelated. For example, the highestlevel of performance may be achieved through system synergies in whichthe physical disposition of the active materials supports the mostcomplete electrochemical reactions. As noted above, in some embodiments,higher performance may correspond to using electrodes that areparticularly thin or that exhibit high surface area. In someembodiments, higher performance may be achieved by using both sides ofone or more electrodes in an electrochemical energy storage device,which may be obtained using a stacked geometry in which a first surfaceof an electrode is positioned proximal to a first solid electrolyte anda second surface of the electrode is positioned proximal to a secondsolid electrolyte.

In some embodiments, an electrochemical energy storage device may thuscomprise several or hundreds of cells, or more, stacked together in amulti-layer arrangement. In some embodiments, a multi-layer arrangementmay comprise a series of stacked electrochemical energy storage cells inwhich the anode of one cell serves as the cathode of the cell stackedadjacent to it. In some embodiments, a multi-layer arrangement maycomprise a plurality of stacked electrochemical energy storage cells inwhich the anode of one cell also serves as the anode of an adjacent celland/or in which the cathode of one cell also serves as the cathode of anadjacent cell.

FIG. 4B provides an overview of a process for making a stackedelectrochemical energy storage device, in accordance with someembodiments, and continues the process depicted in FIG. 4A. Secondelectrode 430 is subjected to a fourth deposition process 433, in orderto form a second solid electrolyte 440 over the second electrode 430.For example, fourth deposition process 433 may correspond to an atomiclayer deposition process to form a ceramic solid electrolyte. Use ofatomic layer deposition processes is advantageous for controlling thethickness of second solid electrolyte 440.

Next, second solid electrolyte 440 is subjected to a fifth depositionprocess 443, such as an atomic layer deposition process, where materialof a third electrode 450 is deposited onto second solid electrolyte 440.Use of atomic layer deposition processes is advantageous for controllingthe thickness of third electrode 450.

It will be appreciated that additional electrolyte/electrode bilayersmay be deposited over an uppermost electrode, similar to the processingdepicted in FIG. 4B, in order to form stacked electrochemical energystorage devices of any desired thickness and number of layers.

In some embodiments, a solid electrolyte may exhibit a crystallinestructure. The solid electrolyte may exhibit a variety of crystal forms,including single crystal and polycrystal. In embodiments where the solidelectrolyte includes crystalline material, the solid electrolyte maytake on different crystal forms, depending on the specific materialconfiguration of the solid electrolyte. FIG. 5 provides a schematicillustration of a first example crystal structure 500 of a solidelectrolyte. It will be appreciated that the crystal structure 500illustrated may correspond to a ceria or zirconium crystal structure,which is provided here as an example only, and that other crystalstructures are possible. For example, in embodiments, the solidelectrolyte may comprise a perovskite ceramic, a ceramic having aperovskite structure, a zirconium ceramic, a ceria-gadolinia ceramic, analumina ceramic, any variant of these, including any doped variant, andany combination of these.

In FIG. 5, various chemical elements make up the crystal structure 500.For example, a first atoms 505, such as metal atoms, may comprise aportion of the crystal structure 500, and second atoms 510, such asoxygen atoms, may comprise a portion of the crystal structure 500.Various defects may be included in the crystal structure 500, which maybe naturally occurring or intentionally introduced. As illustrated,crystal structure 500 includes voids or crystallographic defects 515,which may correspond to vacancy defects, for example, where atoms of thecrystal structure are missing. Voids and crystallographic defects 515may be useful for allowing transmission of oxygen anions through thecrystal structure 500, and provide for the ability of oxygen anions toefficiently migrate through the solid electrolyte. It will beappreciated that other crystal structure features beyond voids orcrystallographic defects such as vacancy defects may also exist in thesolid electrolyte, such as crystallographic defects includinginterstitial defects, line defects, planar defects, bulk defects, andlattice imperfections. An interstitial defect 520 is illustrated. Eachof the voids or crystallographic defects may, in some embodiments,contribute to the ability of ions to efficiently migrate through a solidelectrolyte.

FIG. 6 provides a schematic illustration of another crystal structure600, which includes a first metal 605, oxygen atoms 610, andcrystallographic defects 615. Here, crystallographic defects 615 maycorrespond to vacancy defects. The crystallographic defects 615 may begenerated, for example, by introduction of one or more dopants 620 intothe crystal structure 600. In some embodiments, the dopants 620 andcrystallographic defects 615 may be introduced, for example, during theformation of the crystal structure, such as during an atomic layerdeposition process. In some embodiments, the dopants 620 andcrystallographic defects 615 may be introduced after the crystalstructure 600 is formed, such as by an ion implantation process. Usefuldopants include, but are not limited to, alkali metal dopants, alkalineearth dopants, group 3 dopants, lanthanide dopants, titanium oxidedopants, hydrogen dopants, silver dopants, and/or lead dopants.

In embodiments, when an oxygen anion is added to the crystal structure600 at a crystallographic defect 615, the electronic configuration ofthe crystal structure may change, such as due to the extra electronscarried by the oxygen anion. This configuration may create an unstablestructure, and so the oxygen atoms may rearrange to accommodate theextra material added to the crystal structure and in this way allowoxygen anions to migrate through the crystal structure.

It will be appreciated that, in some embodiments, the electrochemicalenergy storage devices described herein may comprise extremely smalldevices, as the electrodes and electrolyte may comprise layers havingthicknesses as small as about 1 nm. For example, total thicknesses of aunit cell may be as small as about 3 nm, for example, or as large asabout 1 μm. Some unit cell embodiments may comprise larger thicknesses,however, and multi-cell devices may take on any suitable thickness, asthe number of unit cells is virtually without limit. These small unitcell dimensions may provide for a number of the advantageous propertiesof the devices. For example, in embodiments, the devices may exhibitextremely large electrical energy densities when charged, such asgreater than about 10 J/cm³, greater than about 50 J/cm³, greater thanabout 200 J/cm³, or greater than about 500 J/cm³. Although the amount ofenergy stored by a single cell may be small, the dimensionality of thecells may allow many hundreds or thousands or more cells to be includedwithin a small volume, magnifying the overall energy storage capacitygreatly.

Lateral dimensions for the devices, however may take on any suitablevalue, and may (at least) linearly contribute to the amount of energystored by the devices. For example, in some embodiments, the lateraldimensions of the electrodes and the solid electrolyte may be as smallas about 20 nm or less, and may be limited by the deposition abilitiesused during fabrication. Various masking and lithographic processes maybe used, for example, to achieve lateral dimensions as small as about 10nm. In other embodiments, the lateral dimensions may take on largervalues, such as greater than 1 μm, greater than 10 μm, greater than 100μm, greater than 1 mm, greater than 1 cm, or greater than 10 cm. Again,the maximum lateral dimensions achievable may be limited by thedeposition abilities used, but are virtually without limit.

One advantage of such miniaturized energy storage devices is thatmultiple individual devices may be attached to one another to form anenergy distribution network. Energy distribution networks of this naturemay be useful for providing power at the point of load, minimizing powertransmission distances and associated resistive losses and heatgeneration. Energy distribution networks may also be useful forsequestering attached devices from fluctuating electrical loadsengendered by other components. For example, when included in anintegrated circuit, such as in combination with inductive coupling, anenergy distribution network may protect circuits from electricalfluctuations generated by circuit blocks elsewhere on the wafer.

Another advantage is that backup power may be provided in the event ofthe failure of any one of the storage devices in the distributionnetwork, and a portfolio of energy resources may be provided within theconfines of a single system on a chip, for example. Networking of thedevices in an energy distribution may optionally be achieved using oneor more addressable switching transistors, which can be used to isolateindividual blocks or electrochemical energy storage cells/stacks and/orto route current/voltage to components that have had a failure of theirprimary power source.

Optionally, the individual cells may in an energy distribution networkbe connected in series or in parallel and any combinations of series andparallel connections may be made. Such connections may be made highlyconfigurable by the inclusion of switching transistors to set up anddismantle temporary circuit paths.

FIG. 7 provides a schematic overview of a system 700 including a varietyof electrochemical energy storage devices 705, 710, 715. System 700 maycorrespond to a single integrated circuit configured as asystem-on-chip, or may correspond to individual or integratedcomponents, in any configuration. The energy storage devices 705, 710,715 may be used individually as energy sources for one or more othercomponents of system 700, but may also be used in an energy distributionnetwork, as described above, to provide power to any one or morecomponents. In such a configuration, a transistor network may beincluded, for example, to allow for individually switching the flow ofelectrical current from any individual energy storage device 705, 710,715 to any individual component.

As illustrated, however, energy storage devices 705, 710, 715 are shownas separate energy storage devices, providing power to only one or asubset of components of system 700. For example, energy storage device705 is illustrated as providing power to a central processing unitcomprising four individual processing cores. Energy storage device 710is illustrated as providing power to a memory unit, a network unit, andan input/output unit. Energy storage device 715 is illustrated asproviding power to the input/output and a graphics processor. It will beappreciated that the electrical connection providing power from theenergy storage devices to another component may be switchably achieved,such as by using one or more transistors, relays, or other controllableswitching circuits.

FIG. 8 provides a schematic illustration of a multilayer electrochemicalenergy storage device 800. Here, alternating electrodes are connected ina parallel configuration, such that the device comprises a singleparallelized energy storage device. For example, every other electrodeis electrically connected on a first end, while the remaining electrodesare electrically connected on the opposite end. Other configurations arepossible, including series configuration, combined series and parallelconfiguration, and electrical connections to the electrodes may be madeat any suitable position. As illustrated, a first set of electrodesexhibit a first potential (V₁), while a second set of the electrodes,interspersed between the first set of electrodes, exhibit a secondpotential (V₂), such that a potential difference between the electrodesis V₁−V₂. Solid electrolytes are positioned between each adjacentelectrode in FIG. 8.

FIG. 9 provides a cross-sectional schematic illustration of anintegrated circuit 900 including electrochemical energy storage devices905 and 910, positioned over a substrate 915. Each of theelectrochemical energy storage devices 905 and 910 are illustrated asincluding multiple unit cells. A transistor 920 is included in thecircuit 900, including source, drain, and gate elements. Variousinsulating/dielectric layers 925 are included, as well as conductivetraces 930 between various layers and device components. It will beappreciated that the electrochemical energy storage devices may bedistributed and/or networked throughout the integrated circuit asdescribed above.

Inclusion of one or more electrochemical energy storage devices in anintegrated circuit, as illustrated in FIG. 9, may be achieved, inembodiments, because the component materials and characteristics may becompatible with the semiconductor fabrication processes used tomanufacture the integrated circuit. Further, the techniques used to makethe electrochemical energy storage devices, such as atomic layerdeposition, magnetron sputtering, masking, lithography, etc., may bealready utilized in the fabrication of the semiconductor devices, soadditional processing systems and techniques may not have to bedeveloped.

FIG. 10A and FIG. 10B provide cross-sectional schematic illustrations ofa photovoltaic cell 1000 integrated with an electrochemical energystorage device 1030. Photovoltaic cell 1000 may optionally comprise anysuitable photovoltaic material that is compatible with electrochemicalenergy storage device 1030 and the fabrication processes for makingelectrochemical energy storage device 1030. For example, in theembodiments illustrated in FIGS. 10A and 10B, photovoltaic cell 1000comprises a bottom electrode 1005, a p-type silicon layer 1010, ann-type silicon layer 1015 and a top electrode 1020. Electrochemicalenergy storage device 1030 comprises multiple layers of electrodes andelectrolytes, for example similar to multilayer electrochemical energystorage device 800 described above. A first set of electrodes ofelectrochemical energy storage device 1030 is illustrated as inelectrical communication with top electrode 1020 and a second set ofelectrodes of electrochemical energy storage device 1030 is illustratedas in electrical communication with bottom electrode 1005. A load 1025is also illustrated as electrically connected between bottom electrode1005 and top electrode 1020.

In FIG. 10A, the electrochemical energy storage device 1030 ispositioned directly below and optionally in contact with bottomelectrode 1005. Such a configuration may be desirable for example, toallow the first electrode of electrochemical energy storage device 1030to be deposited directly on bottom electrode 1005 during themanufacturing process. Other examples are possible, such as where aninterleaving material, such as an insulator, semiconductor, or otherconducting material is positioned between bottom electrode 1005 andelectrochemical energy storage device 1030. Additionally, differentphysical arrangements of the photovoltaic cell 1000 and electrochemicalenergy storage device 1030 are contemplated. As an example, in FIG. 10B,the photovoltaic cell 1000 and electrochemical energy storage device1030 are positioned side-by-side. Such a configuration may be desirableto allow electrochemical energy storage device 1030 to be positionedwithin the spaces between adjacent photovoltaic cells, for example.Further arrangements are contemplated, including where theelectrochemical energy storage device 1030 and photovoltaic cell 1000are independent components and where the electrochemical energy storagedevice 1030 is used as a standalone energy storage backup module.

It will be appreciated that providing electrochemical energy storagedevices in electrical communication with photovoltaic cells may beuseful, in embodiments, for modulating the output of the photovoltaiccell and minimizing variability in cell output. Additionally, whenexposed to light, the excess electrical energy generated by thephotovoltaic cell may be used to charge the electrochemical energystorage device to store the excess energy. The stored energy may then beprovided by the electrochemical energy storage device as voltage outputduring non-peak times, such as during the night or on cloudy days, forexample. Including the electrochemical energy storage devices directlyon the same structure as the electrochemical cell is furtheradvantageous for simplifying construction, integration, shipping, etc.Additionally, the use of the electrochemical energy storage devicesdescribed herein may be beneficial, for example, as the electrochemicalenergy storage devices may have large power densities and can receiveand provide large current densities as needed, without damaging theelectrochemical energy storage devices or degrading their storagecapacities. Further, the electrochemical energy storage devices mayexhibit large cycle lives without resulting in component degradation orcapacity loss, making them beneficial for use in these photovoltaicapplications as well as other energy storage applications.

Additional related description may be found in U.S. patent applicationSer. No. 13/536,029, filed on Jun. 28, 2012, and U.S. ProvisionalApplication 61/502,797, filed on Jun. 29, 2011, which are herebyincorporated by reference in their entireties.

The present invention may be further understood by reference to thefollowing non-limiting examples.

A. Architecture

Like batteries, the solid-state electrochemical energy storage devicesand systems described herein make use of conduction of ions through anelectrolyte. For example, the disclosed electrochemical energy storagedevices and make use of reversible electrochemical redox reactions thattake place at the electrodes with ions that pass through theelectrolyte. In the disclosed electrochemical energy storage devices,these reversible redox reactions can occur without limit, and permitfull discharge without damage. In some embodiments, an electrochemicalenergy storage device comprises a simple construction, where twoelectrodes are separated by a solid-state electrolyte.

B. Temperature

Unlike battery chemistries such as lead/acid and lithium-ion,electrochemical energy storage devices described herein are notrestricted by temperature and remain capable of operating within a widerange of temperatures, such as, for example between about −100° C. andabout 700° C., although some embodiments may exhibit a certain amount oftemperature sensitivity. It will be appreciated that the electrochemicalenergy storage devices of some embodiments can withstand thistemperature range due to the use of ceramic electrolytes instead ofliquid, gel, or polymer electrolytes. It will be appreciated that theceramic materials used as electrolytes herein are not commonly seen torepresent electrolytes at ambient temperatures when in bulk, but ratheras dielectrics through which neither electrons nor positive ions canmove.

C. Electrolyte Materials & Scale

In some embodiments, the disclosed electrochemical energy storagedevices use specially doped and extremely thin ceramic films, where theceramic presents a crystalline lattice with oxygen vacancies throughwhich oxygen ions can flow to interface with the electrodes. The lengthscales used to achieve the conductivity of oxygen ions vary somewhatfrom material to material. In some embodiments, the thickness of theceramic solid-state electrolyte is between about 30 nm and about 100 nm.If the electrolyte exceeds its limits, it reverts to a dielectric ratherthan an electrolyte, and thus will not function for energy storage, andso in no case does the thickness equal or exceed 1 μm. Conversely, ifthe electrolyte is too thin, opportunities exist for catastrophicfailure by shorting out, such as due to surface roughage orelectrostatic discharge from one electrode to the other through theelectrolyte.

D. Doping

Basic ceramic materials such as alumina and zirconium in pure form maypresent monolithic and nonconductive surfaces to the electrodes if usedin an electrochemical energy storage device. In order to present alattice that contains the oxygen vacancies useful for ionicconductivity, some pure ceramic materials may require doping. The dopingmay, for example, create lattice imperfections, crystallographicdefects, or ion carrier sites that the extremely small thickness scalecan exploit. In some cases, this amounts to creating an alloy, such aswhere the dopant is as much as 50% of the material. Na+ doped alumina(β-alumina), is an example.

E. Energy Density & Charge

Due to the small amounts of material incorporated into theelectrochemical energy storage devices at the scales used in variousembodiments, only small amounts of charge will be stored, even with arelatively high energy density. In certain embodiments, however, such asintegrated into electronic circuitry in semiconductor chip fabrication,this small amount of charge can provide power at the point of load on aninstantaneous basis. In addition, inductive coupling from a nearbysource can be used in some embodiments to continuously recharge theelectrochemical energy storage devices.

In more general applications, such as replacement batteries for aconsumer electronic device, such as a smart phone or laptop battery,embodiments may require multiple layers or cells to provide the neededcurrent. For example, multiple layers of electrochemical energy storagedevices may be constructed on top of one another to achieve largeramounts of charge storage. Given the small thicknesses, many thousandsof layers of electrodes and solid-state electrolytes can, inembodiments, be constructed within common battery pack sizes, such as onthe order of about 1 cm to about 10 cm. Techniques, such as advancedcommercial magnetron sputtering, atomic layer deposition, and othernanoscale deposition techniques allow economical fabrication of suchmulti-celled devices.

In a specific embodiment, a combination of two electrodes and oneelectrolyte layer constitutes a single cell. Optionally, theelectrochemical energy storage device may consist of a single cell orless than about 50 cells, such as in a continuous stackingconfiguration. The electrochemical energy storage device may optionallybe reduced to a depth that is commensurate with complete integrationinto a wafer based microcircuit where the electrochemical energy storagedevice shares the same wafer as the active circuitry.

F. Field Specifics

In some embodiments, multi-celled electrochemical energy storage devicescomprising multiple layers of electrodes in between electrolytes maydeliver even more energy storage/unit size than lithium-ion can attain.In embodiments, replacement devices can use drop-in replacement formfactors, where the electrochemical energy storage device may measure afew microns to a few mm in thickness or larger, with the remaining formconsisting of a case enabling direct replacement in existing devices.Using inductive charging, some embodiments may store enough charge thatelectronic devices would never need direct, wired, charging beyond thefirst time.

G. Chip Integration

As described in more detail below, many batteries identified as“solid-state” batteries are not truly solid-state. For example, theelectrolyte in these batteries typically comprises a gel or a powder ora colloidal suspension. It will be appreciated that these materialscannot withstand large temperature variations used in commonsemiconductor fabrication process, and thus are incompatible withintegrated circuits, for example. Gel electrolytes behave analogously toaqueous electrolytes where crystallinity is not present and ions are notbound but are free to pass across the fluid or semifluid medium,impelled by electrical forces. Other devices may have a crystallineelectrolyte, but use a liquid electrode.

In contrast, the electrochemical energy storage devices described hereinmake use of rigid crystalline lattice structures. For example, defectsmay be deliberately and artfully introduced to the crystal lattice inorder to provide transient pathways for the movement of ions. Thesepathways may be engineered and organized by various techniques involvingthe introduction of chemical dopants or by the imposition of strain orby the application of outside forces, either transient or persisting.Such forces tend to deform the lattice structure such that paths forionic migration become present, for example. These design strategiesexecuted on the molecular and supramolecular level may be used toregulate the volume of ionic flow, and the process may involvebeneficial nonlinearities with respect to ionic volume that may beexploited.

H. Electrochemical Energy Storage Device Architecture

In a solid electrolyte, such as a thin ceria stabilized zirconia layersituated between two metal or metal oxide electrodes, oxygen ions mayshuttle between the electrodes bearing opposing charges. Without wishingto be bound by any theory, the inventors believe that the positive ionsmove by traversing through the interstices of a fairly rigid crystallinelattice of extremely limited depth (thin-film), but rich in oxygenvacancies, and it is the oxygen vacancies that permit the free movementof positive ions. A trade-off exists between high ionic conductivity andmultiple-layer requirements. The movement of ions through thesolid-state electrolyte may also be further tuned by the imposition ofexternal stresses, such as those caused by a bi- or multi-layerelectrolyte, that deform the lattice and widen the passageways for ionicmovement. In either stressed or unstressed cases, the ions participatingin electrochemical storage act as replacements for atoms distributedwithin the electrolyte, and these ions hop from site to site.

I. Temperature Range and Integrated Circuit Integration

The completely solid, gel-free electrochemical energy storage devicesdisclosed herein are capable of withstanding very large temperaturevariations. For example, some embodiments may be useful between about−100° C. and about 800° C. In addition, the devices, due to the lack ofliquid or gel materials, may be rugged and capable of integration intoactive semiconductor circuitry. In terms of size reduction, this canreduce, for example, the size of an integrated circuit, such as acentral processing unit, by about 70%, due to the elimination of pinconnectors and attendant circuitry, in some embodiments, which may beaccompanied by a corresponding reduction of heat generation. Inaddition, the electrochemical energy storage devices, such as whencoupled inductively, permit redundant instantaneous power at point ofload.

Additionally, the electrochemical energy storage can take the form, insome embodiments, of a network of cells. Printed conductive traces mayconvey the stored energy to its destination and switching matrices mayallow for powering any of the circuit components by any of the cells, inany combination. For example, some cells may power logic circuits, whileother cells may power mixed signal circuits.

Switching between and among energy storage cells may take the form ofstar and hub architectures, redundant rings, or mesh networks with orwithout intelligence. Such architectures may serve to support power atthe point of load design strategies or islanding of defective cells oradjustments in voltage and current by making cell to cell connectionswitchable.

It will be appreciated that, because of the flexibility afforded by thematerials and architectures used in the electrochemical energy storagedevices, an array of cells may be planar, three dimensional, or maycomprise a succession of stacked planes, for example. In addition,planar inductors may, optionally, be incorporated along with the storagecells such that islands of energy storage may be inductively coupledwith one another, reducing the number of conductive pathways and themass and volume of an integrated circuit incorporating energy storage.

In some embodiments, the materials that comprise an electrochemicalenergy storage device may be rendered rigid and unyielding or flexible,depending upon the thickness of the material and the presence or absenceof porosity within it. Energy storage may thus be incorporated inflexible thin films such as displays or thin film photovoltaic cells orin energy harvesting devices dependent upon the movement of membranes togenerate electrical power, for example. In addition, caseless batteriesmay constructed in which the electrodes and electrolytes providestructural integrity to the batteries. In some embodiments, theelectrochemical energy storage devices may also be integrated withplanar energy harvesting radio frequency antennas or with generator andactuator MEMS elements, so that microelectromechanical energy storage,power electronics, and signal processing may be incorporated into asingle wafer with a high degree of synergy and integration among theseparate elements.

J. Gel-Free

Embodiments of the present invention relate to solid-stateelectrochemical energy storage devices and methods of making solid-stateelectrochemical energy storage device in which components of the devicesare truly solid-state (i.e., they do not comprise a gel). Thesolid-state battery nomenclature is not new but it has always beenmisleading in the prior art. Many “solid-state batteries” utilize eithergels or in some case powders for the electrolyte layers and neverhomogenous, consolidated solid materials that can integrate intosemiconductor chips directly, for example. Gel materials prohibit bothincorporation within VLSI/ULSI chips, and restrict temperature ranges toapproximately ambient.

True solid-state electrolyte layers have been utilized in solid oxidefuel cells. When used in a solid oxide fuel cell, solid-stateelectrolyte layers normally conduct ions at a practical rate only atextremely elevated temperature, such as exceeding 600° C. However, thesolid electrolyte layers described herein exhibit high ionicconductivity, which may approximate or exceed that of liquid or gelelectrolytes, even at ambient or near ambient temperatures. The ambienttemperature ionic conduction exploited herein also offers a furtheradvantage of preserving high electrical resistance and dielectricstrength, which are commonly sacrificed in solid-state supertonicconductors at high temperatures.

In exemplary embodiments, gaseous oxygen (O₂) and/or oxygen ions (e.g.,O⁺ or O²⁻) are responsible for charge transport and formation of theelectrochemical bonds (redox) by which electrical charge is stored andconserved. A number of transport mechanisms may invoke the passage ofoxygen ions through the crystalline structure of the solid electrolytelayer. For example, oxygen vacancies within the crystal lattice may bean important source of ion transport.

It will be appreciated that oxygen vacancies may represent defects, andmay be present when the ceramic has been doped with another chemicalwhich results in a departure from the regularity of the crystallinestructure present in the pure ceramic. Such defects may be analogous to“holes” in P type semiconductors, for example. It may be advantageous ifthe ceramic and/or the dopant contains the element that will be ionized,and some of that element may be dislodged from the crystal structure.Additional ions may be drawn from the anode or the cathode, or from theatmospheric air if oxygen ions participate in the electrochemicalreactions.

The ionic conduction modes in ceramic electrolytes are very differentfrom those present in aqueous or polymer electrolytes where nocrystalline lattice is present and where ions are released by means ofelectrolysis or simply pass through the fluid medium from theelectrodes. In true solid electrolytes, as opposed to gels, bothchemistry and mechanical forces play a role in ionic migration as doesthe phase of the crystalline structure, i.e. whether it is amorphous orcubic.

The addition of dopants alone may not provide a high degree of ionicconductivity under ordinary circumstances, and some solid electrolytematerials will not conduct ions at all at macro scale thicknesses and atambient temperatures, for example. In some embodiments, violent flexuresand dislocations of the lattice structure are required to supportinterstitial movements of ions.

Such flexures may take the form of phonons, that is, thermally inducedperiodic oscillations at audio frequencies or more enduring surfacestrains imposed by the fabrication process or by the presence ofmicro-actuators such as piezoelectric elements that exert shear forces.Either mechanism may provide spaces through which positive ions may betransported.

It will be appreciated that zirconia and other ceramics may be suitableas solid electrolytes. In some embodiments, useful ceramics includedoped ceramics. For example, calcium, magnesium, yttrium, aluminum, andceria stabilized zirconias may also be useful solid electrolytes.

K. Fabrication

In embodiments, a solid-state electrolyte layer, which may be aconsolidated structural layer, offers many performance advantages. Forexample, the structural integrity conferred by a solid electrolytecombined with solid electrodes may eliminate the need for an externalcase, in some embodiments. For example, in one embodiment, theelectrochemical energy storage device can be naked, i.e., not associatedwith any other structural materials. In some embodiments, theelectrochemical energy storage device may be built up as an integralcircuit element within a larger microcircuit with wafer fabricationtechniques. These examples may not possible with conventional batterytechnologies. The solid-state electrochemical cells described hereinalso may possess inherent physical robustness and a high immunity toshock, vibration, and temperature extremes. In addition, the solid-stateelectrochemical energy storage devices described herein are highlyscalable such that they may be closely coupled to such entities as MEMSdevices and microfluidic systems.

In exemplary embodiments, a solid-state electrochemical energy storagedevice becomes, in essence, another circuit element in an integratedcircuit and facilitates the realization of optimal circuit paths andgrounding schemes because it lends itself to strategic placement withinthe overall circuit. In some embodiments, this can eliminate as much as70% of the circuitry (e.g., the portion served by power pins) inexisting VLSI/ULSI chips, greatly reducing size and heat generation.

L. Point of Load Power and Inductive Charging

Solid-state construction has implications that are as potentially asrevolutionary with respect to electrical charge storage as they havebeen to active circuitry when transistors largely replaced vacuum tubes(thermionic valves) more than a half-century ago. For example, just astransistors invoke different mechanisms for controlling the passage ofcurrent through a circuit and realization of voltage and current gain,solid-state electrochemical energy storage devices may utilize uniquemechanisms for storing and releasing electrical charge at the point ofload. Also importantly, solid-state electrochemical energy storagedevices exhibit an ability to charge rapidly by inductive coupling(rapidity due to the ability to resist overcharging), permittingwireless charging and potentially eliminating need for nearby powersources entirely.

It should be understood that, in various embodiments, the solid-stateelectrochemical energy storage devices described herein categoricallyreference redox reactions. In this text, oxygen may stand for any ofthose. In exemplary embodiments, charge storage may be achieved throughtruly reversible redox reactions occurring adsorptively some littledistance into the depths of the electrode layer. That depth may be inthe angstroms or into the low nanometers, and, to be more specific, lessthan 10 nanometers. Oxygen ions may form the basis of theelectrochemical reactions.

Without wishing to be bound by any theory, oxygen ions may enter andleave the electrodes during the charge/discharge cycles, and areadsorbed to depths of about 0.2 nm to about 10 nm, such as about 0.5 nm,about 1 nm, about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm,about 7 nm, about 8 nm, about 9 nm, about 10 nm, or any combination ofranges between any of these specific values. In exemplary embodiments,the electrodes themselves range in overall depth/thickness from betweenabout 7 nm to about 50 nm.

Uniquely, multiple redox reactions may be invoked, and successivelyhigher oxides may be formed at successively higher input voltages. Forexample, in some embodiments, exemplary electrode materials comprise,consist of, or consist essentially of elemental metals or metal oxidescapable of forming a sequence of oxides of progressively greatermolecular weight. These may include, for example, monoxides, dioxides,trioxides, tetroxides, pentoxides, hexoxides, heptoxides, and so on. Insome embodiments, hydrides or nitrides may be substituted for oxides.Work functions for candidate materials may, for example, range betweenabout 4 electron volts and about 5 electron volts and may also includevalues between these limits.

In exemplary embodiments, electrolyte layers comprise ceramiccompositions supporting expeditious transfer of positive oxygen ionsfrom the anode to the cathode or from the cathode to the anode atambient or near ambient temperatures. Transfer rates optionally rangefrom about 10 to about 50 Siemens per centimeter, and these rates may begreater in architectures where the electrolyte thickness is less thanabout 58 nm. Useful ceramic compositions include a number of perovskitesand perovskite-related oxides, as well as many zirconium ceramics, suchas zirconia-scandia, Zr_(1-x)Sc_(x)O_(2-δ) and the cheaper zirconiumstabilized by yttria, and ceria-gadolinia, Ce_(1-x)Gd_(x)O_(2−δ) (CGO),alumina and β-alumina formulated with a number of dopants such asceramic forms of Na⁺, K⁺, Li⁺, Ag⁺, H⁺, Pb₂ ⁺, Sr₂ ⁺ or Ba₂, TiO, TiO₂,Ti₂O₃, etc.

M. Evacuated Electrolyte

Alternatively, the electrolyte layer may be largely evacuated, and theresulting cavity may be supported with minute spacers measuring betweenabout 20 nm and about 100 nm, for example. In such instances, the cavityis optionally filled with gaseous oxygen (or hydrogen or nitrogen) at apressure of about 0.1 bar, or about 0.2 bar or about 0.3 bar, or atfractional or intermediate values or ranges between these statednumbers.

In one embodiment, the gas may, for example, be ionized by a pair oflateral electrodes that impose a transient high voltage on the gas, suchas a voltage that imparts an electric field of sufficient strength toionize the gas.

N. Enhanced Ionic Conductivity Dependencies

Thin-film scale and temperatures. Invoking high ionic conductivity forpurposes of fabricating electrochemical energy storage devices viathin-film deposition of the solid-state electrolytes may involve twoaspects. The first, thickness of the film, may dominate at all enhancedionic conductivity temperatures. Temperature itself plays a significantrole, especially at thicker (but still thin) films.

Enhanced ionic conductivity in the sense of orders of magnitude greaterthan bulk ionic conduction for the above mentioned solid-stateelectrolytes is exhibited below a particular thickness, which may varyfrom material to material. As an example, the enhancement forelectrolytes in the zirconium family begins at below about 700 nm.Thicker than that, bulk material characteristics dominate and thewell-known Arrhenius formula apply. In smaller thickness electrolytes,the enhanced ionic migration is observed and embodiments describedherein may make use of this advantageous property.

Temperature-dependent enhanced ionic conductivity is observed, inembodiments, when the interface conductance is greater than that of thebulk—that is, thinner than a threshold of about 700 nm. Invoking ambienttemperature performance requires films with acceptable ranges, forexample, lower than about 62 nm, in some embodiments. The range from 30nm to 1 nm may provide exceptional performance, with 1 nm providingnegligible resistance to ionic flow while still continuing electronholdoff.

Strained interfaces. Another technique for invoking enhanced ionicmigration involves a strained membrane or film. This may be achieved viadeposition of heterogeneous electrolyte materials in sandwiched form,such as perovskites/zirconium compounds/perovskites, or the reverseorder. Films of substantially less than 1 μm may be useful for achievingthe enhanced ionic migration in this way.

Advantageous aspects of the described electrochemical energy storagedevices include, but are not limited to:

-   -   A true, gel-free, solid-state electrochemical energy storage        device with solid metallic or metal oxide electrodes and solid        electrolyte layers having structural as well as electrical        properties. The electrolyte layers consist of glass or ceramic        compositions capable of supporting massive ionic migrations at        the dimensions specified, and at ambient or near ambient        temperature.    -   Bi-layer electrodes capable of forming oxides and successions of        higher oxides in the presence of an electrical charge.    -   An elementary unit consisting of a single cell comprised of two        electrodes and an electrolyte layer all of solid, consolidated        construction.    -   A structural electrochemical energy storage device that is        self-supporting and requires no external case.    -   Methods of construction such as atomic layer deposition and        advanced commercial sputtering that permit full integration of        storage into integrated circuits.    -   An elementary unit consisting of two electrodes separated by        spacers or an open framework which is constructed on the        nano-scale and affords a volume for containing gaseous oxygen as        a source of ions.    -   A means of ionizing the confined oxygen.    -   A cell thickness of less than about 200 nanometers and as little        as about 30 nanometers and any intermediate value.    -   An electrode thickness of less than about 50 nanometers and more        than about 5 nanometers.    -   An electrolyte layer thickness of less than about 150 nanometers        and no less than about 20 nanometers.    -   A multi-layer construction ranging from 2 cells up to thousands        of cells and any number in between.    -   A multi-layer construction having any combination of series and        parallel connections between and among cells.    -   A modular design incorporating dispersed energy storage units.    -   A switching network for addressing dispersed energy storage        units.    -   A capability of undergoing full discharge without incurring        damage or degradation.    -   A formula that enables selection of appropriate electrode        materials based on a variety of factors including work function,        oxidation number, performance under various temperatures, and        availability.    -   A formula that enables the selection of appropriate solid        electrolyte materials based on factors including atomic voids        and/or band gaps and membrane stress that permit oxygen ion        migration through the electrolyte, and performance under various        temperatures.

It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this applicationand scope of the appended claims.

What is claimed is:
 1. A Faradaic solid-state energy storage devicecomprising: a first electrode, wherein the first electrode has a firstthickness greater than 1 nm and less than or equal to 80 nm, and whereinthe first electrode comprises a first redox-supporting transition metal,an oxide of the first redox-supporting transition metal, or acombination of the first redox-supporting transition metal and the oxideof the first redox-supporting transition metal; a solid electrolytepositioned in direct contact with the first electrode, wherein the solidelectrolyte has a second thickness greater than 1 nm and less than orequal to 500 nm, and wherein the solid electrolyte comprises asolid-state, oxygen ion conducting ceramic electrolyte, wherein thesolid-state, oxygen ion conducting ceramic electrolyte has a crystalstructure including vacancies that permit conduction or migration ofoxygen ions through the crystal structure; and a second electrodepositioned in direct contact with the solid electrolyte, wherein thesecond electrode has a third thickness greater than 1 nm and less thanor equal to 80 nm, and wherein the second electrode comprises a secondredox-supporting transition metal, an oxide of the secondredox-supporting transition metal, or a combination of the secondredox-supporting transition metal and the oxide of the secondredox-supporting transition metal.
 2. The Faradaic solid-state energystorage device of claim 1, wherein the first electrode is dispersed on afirst electrically conductive supporting substrate, or wherein thesecond electrode is dispersed on a second electrically conductivesupporting substrate, or both.
 3. The Faradaic solid-state energystorage device of claim 1, wherein the first electrode, the secondelectrode, and the solid electrolyte are independently fabricated usinga controllable deposition method including one or more techniquesselected from the group consisting of: atomic layer deposition,magnetron sputtering, sputter deposition, molecular beam epitaxy, pulseddeposition, and chemical vapor deposition.
 4. The Faradaic solid-stateenergy storage device of claim 1, wherein the first thickness and thethird thickness are independently between 10 nm and 80 nm and whereinthe second thickness is between 15 nm and 500 nm.
 5. The Faradaicsolid-state energy storage device of claim 1, wherein the firstredox-supporting transition metal, the second redox-supportingtransition metal, or both the first redox-supporting transition metaland the second redox-supporting transition metal comprise a transitionmetal having two non-zero oxidation states.
 6. The Faradaic solid-stateenergy storage device of claim 1, wherein the first redox-supportingtransition metal and the second redox-supporting transition metal havedifferent oxidation states.
 7. The Faradaic solid-state energy storagedevice of claim 1, wherein the first redox-supporting transition metaland the second redox-supporting transition metal are independently Co,or Ni.
 8. The Faradaic solid-state energy storage device of claim 1,wherein the first redox-supporting transition metal comprises ruthenium,wherein the second redox-supporting transition metal comprisesruthenium, or wherein both the first redox-supporting transition metaland the second redox-supporting transition metal comprise ruthenium. 9.The Faradaic solid-state energy storage device of claim 1, wherein thefirst redox-supporting transition metal and the second redox-supportingtranstion metal exhibit between 3 and 6 positive oxidation states. 10.The Faradaic solid-state energy storage device of claim 1, wherein thesolid electrolyte has a temperature of between 50° C. and 600° C., andwherein the solid electrolyte permits conduction or migration of oxygenions through the solid electrolyte for participation in redox reactionsat the first electrode and the second electrode.
 11. The Faradaicsolid-state energy storage device of claim 1, further comprising: asecond solid electrolyte positioned in direct contact with the secondelectrode, wherein the second solid electrolyte has a fourth thicknessgreater than 1 nm and less than or equal to 500 nm, and wherein thesecond solid electrolyte comprises a second solid-state, oxygen ionconducting ceramic electrolyte, wherein the second solid-state, oxygenion conducting ceramic electrolyte has the crystal structure includingvacancies that permit conduction or migration of oxygen ions through thecrystal structure; and a third electrode positioned in direct contactwith the second solid electrolyte, wherein the third electrode has afifth thickness greater than 1 nm and less than or equal to 80 nm, andwherein the third electrode comprises a third redox-supportingtransition metal, an oxide of the third redox-supporting transitionmetal, or a combination of the third redox-supporting transition metaland the oxide of the third redox-supporting transition metal.
 12. TheFaradaic solid-state energy storage device of claim 1, wherein the firstredox-supporting transition metal comprises manganese, wherein thesecond redox-supporting transition metal comprises manganese, or whereinboth the first redox-supporting transition metal and the secondredox-supporting transition metal comprise manganese.
 13. The Faradaicsolid-state energy storage device of claim 1, wherein the firstelectrode has a first oxidation state and the second electrode has asecond oxidation state, and wherien a difference between the firstoxidation state and the second oxidation state provides a storedelectrical energy density of between 10 J/cm³ and 750 J/cm³.
 14. TheFaradaic solid-state energy storage device of claim 1, wherein thesolid-state, oxygen ion conducting ceramic comprises yttria-stabilizedzirconia (YSZ) having the crystal structure including vacancies thatpermit conduction or migration of oxygen ions through the crystalstructure.
 15. A method of making a Faradaic solid-state energy storagedevice, the method comprising: depositing a first electrode on asubstrate, wherein the first electrode has a first thickness greaterthan 1 nm and less than or equal to 80 nm, wherein the first electrodecomprises a first redox-supporting transition metal, an oxide of thefirst redox-supporting transition metal, or a combination of the firstredox-supporting transition metal and the oxide of the firstredox-supporting transition metal, and wherein depositing the firstelectrode includes depositing using a first controllable depositionmethod; depositing a solid electrolyte on the first electrode, whereinthe solid electrolyte has a second thickness greater than 1 nm and lessthan or equal to 500 nm, wherein the solid electrolyte comprises asolid-state, oxygen ion conducting ceramic electrolyte, wherein thesolid-state, oxygen ion conducting ceramic has a crystal structureincluding vacancies that permit conduction or migration of oxygen ionsthrough the crystal structure, and wherein depositing the solidelectrolyte includes depositing using a second controllable depositionmethod; and depositing a second electrode on the solid electrolyte,wherein the second electrode has a third thickness greater than 1 nm andless than or equal to 80 nm, wherein the second electrode comprises asecond redox-supporting transition metal, an oxide of the secondredox-supporting transition metal, or a combination of the secondredox-supporting transition metal and the oxide of the secondredox-supporting transition metal, and wherein depositing the secondelectrode includes depositing using a third controllable depositionmethod.
 16. The method of claim 15, further comprising: depositing asecond solid electrolyte on the second electrode, wherein the secondsolid electrolyte has a fourth thickness greater than 1 nm and less thanor equal to 500 nm, wherein the second solid electrolyte comprises asecond solid-state, oxygen ion conducting ceramic electrolyte, whereinthe second solid-state, oxygen ion conducting ceramic electrolyte has acrystal structure including vacancies that permit conduction ormigration of oxygen ions through the crystal structure, and whereindepositing the second solid electrolyte includes depositing using afourth controllable deposition method; and depositing a third electrodeon the second solid electrolyte, wherein the third electrode has a fifththickness greater than 1 nm and less than or equal to 80 nm, wherein thethird electrode comprises a third redox-supporting transition metal, anoxide of the third redox-supporting transition metal, or a combinationof the third redox-supporting transition metal and the oxide of thethird redox-supporting transition metal, and wherein depositing thethird electrode includes depositing using a fifth controllabledeposition method.
 17. The method of claim 15, wherein the firstredox-supporting transition metal and the second redox-supportingtransition metal independently comprise ruthenium, manganese, cobalt, ornickel, and wherein the solid-state, oxygen ion conducting ceramicelectrolyte comprises yttria-stabilized zirconium (YSZ) having thecrystal structure including vacancies that permit conduction ormigration of oxygen ions through the crystal structure.
 18. The methodof claim 15, further comprising initiating redox reactions at the firstelectrode and the second electode to reversibly establish storedelectrical energy having a density of between 10 J/cm³ and 750 J/cm³.19. A Faradaic solid-state energy storage device comprising: a firstelectrode, wherein the first electrode has a first thickness greaterthan 1 nm and less than or equal to 80nm, and wherein the firstelectrode comprises a cobalt oxide or a nickel oxide; a solidelectrolyte positioned in direct contact with the first electrode,wherein the solid electrolyte has a second thickness greater than 1 nmand less than or equal to 500 nm, and wherein the solid electrolytecomprises a solid-state, oxygen ion conducting yttrium stabilizedzirconium (YSZ) electrolyte, wherein the solid-state, oxygen ionconducting YSZ electrolyte has a crystal structure including vacanciesthat permit conduction or migration of oxygen ions through the YSZ; asecond electrode positioned in direct contact with the solidelectrolyte, wherein the second electrode has a third thickness greaterthan 1 nm and less than or equal to 80nm, and wherein the secondelectrode comprises cobalt oxide or nickel oxide; a plurality ofadditional solid electrolytes, each of the plurality of additional solidelectrolytes positioned in direct contact with one or two electrodes,wherein the plurality of additional solid electrolytes eachindependently have thicknesses greater than 1 nm and less than or equalto 500 nm, and wherein the plurality of additional solid electrolytescomprise the solid-state, oxygen ion conducting ceramic electrolyte; anda plurality of additional electrodes, each of the plurality ofadditional electrodes positioned in direct contact with one or two ofthe plurality of additional solid electrolytes, wherein the plurality ofadditional electrodes each independently have thicknesses greater than 1nm and less than or equal to 80 nm, and wherein the plurality ofadditional electrodes each independently comprise cobalt oxide or nickeloxide.
 20. The Faradaic solid-state energy storage device of claim 19,wherein oxidation states of the cobalt oxide or the nickel oxidealternate from electrode to electrode.